These are instructions on how to find the firmware and baseband version (modem firmware) your iPhone is currently running.
Step One
Press to launch Settings from your Springboard.
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Step Two
Press to select General from the Settings Menu.
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Step Three
Press to select About from the General Settings Menu.
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Step Four
From the about screen you can find your firmware version under the Version label.
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Scroll down and you can find your baseband version under the Modem Firmware label.
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